|Publication number||US7347533 B2|
|Application number||US 11/017,471|
|Publication date||Mar 25, 2008|
|Filing date||Dec 20, 2004|
|Priority date||Dec 20, 2004|
|Also published as||DE602005027431D1, EP1671798A2, EP1671798A3, EP1671798B1, US20060132543|
|Publication number||017471, 11017471, US 7347533 B2, US 7347533B2, US-B2-7347533, US7347533 B2, US7347533B2|
|Inventors||Scott A. Elrod, John S. Fitch, David K. Biegelsen|
|Original Assignee||Palo Alto Research Center Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (22), Non-Patent Citations (4), Referenced by (7), Classifications (14), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present application relates to printheads and methods of making printheads and more particularly to employing manufacturing concepts for low cost printhead production.
Ink jet printheads, and in particular drop-on-demand ink jet printheads, are well known in the art. The principle behind an piezo ink jet printhead is the displacement of an ink chamber and subsequent emission of ink droplets from the ink chamber through a nozzle. A driver mechanism is used to displace the ink in the ink chamber. The driver mechanism typically consists of a transducer (e.g., a piezoelectric component) bonded to a thin diaphragm. When a voltage is applied to a transducer, the transducer attempts to change its planar dimensions, but, because it is securely and rigidly attached to the diaphragm, bending occurs. This bending displaces ink in the ink chamber, causing the flow of ink both through an inlet from the ink supply to the ink chamber and through an outlet and passageway to a nozzle. In general, it is desirable to employ a printhead geometry that permits multiple nozzles to be positioned in a densely packed array. However, the arrangement of ink chambers and coupling of ink chambers to associated nozzles is not a straight forward task, especially when compact ink jet array printheads are sought.
The printing industry is continually seeking to decrease the cost of printing systems and to improve the printing quality. In order for piezoelectric inkjet printing devices to remain competitive, for example in markets currently addressed by xerography, the cost for such printheads need to decrease.
While various cost saving approaches have been addressed, many steps of printhead manufacturing employs procedures specifically designed for such devices and use labor intensive and costly processes.
An example of an existing drop on demand ink jet printhead is taught by U.S. Pat. No. 5,087,930. This patent was designed to enhance the packing density of the pressure chambers, ink supply channels leading to the pressure chambers and offset channels in the printhead. However, as can be seen, the printhead is formed using specific manufacturing processes for the printhead including diffusion bonding and braising. A drawback of this manufacturing system as well as others is the requirement of using processes that are formed specifically for the printhead industry. Since such processes are designed specifically for the printhead industry, only a relatively small number of companies and/or persons have the expertise to manufacture the printheads. It is therefore worthwhile to use technology that has a wider base of use and/or infrastructure for the manufacture of printheads resulting in an increased cost savings.
In accordance with one aspect of the present exemplary embodiment, a printhead includes a printed circuit board having at least one base layer, with at least electrical trace, at least one fluidic passage and at least one fluidic chamber as part of the printed circuit board. The electrical trace, fluidic passage and fluidic chamber are all formed using printed circuit board manufacturing processes. An integrated circuit control chip is attached to the printed circuit board using known printed circuit board techniques. At least one fluidic actuator arrangement and aperture plate are attached to the printed circuit board using known PCB attachment processes.
Printed circuit boards are known to carry electronic circuits formed by mounting electronic components on a non-conductive substrate, and creating conductive connections between them. The creation of the circuit patterns is accomplished by using both additive and subtractive methods. The conductive circuit is generally copper, although aluminum, nickel, chrome and other metals or conductors may also be used. There are three basic varieties of printed circuit boards including single-sided, double-sided, and multi-layered. The spatial and density requirement and circuitry complexity determine the type of board produced.
Production of printed circuit boards involve the plating and selective etching of flat metal circuits supported on a non-conductive substrate/base, such as a sheet of plastic. Production begins with a sheet of plastic laminated with a thin layer of copper foil. Holes (such as vias) are drilled through the board using an automated drilling machine or other hole-making device including for example, lasers. Holes are used to mount electronic components in the board and to provide a conductive circuit from one layer of the board to another. Following the drilling, the board is cleaned and etched to promote good adhesion and is then plated with an additional layer of metal. Since the holes are not conductive, electroless metal plating may be employed to provide a thin continuous conductive layer over the surface of the board and through the holes. Following plating, a plating resist is applied and photo-imaging or patterning is used to create the circuit design. Metal may then be electroplated on the board to its final thickness. A thin layer of tin lead solder or pure tin is plated over the metal as an etch resist. The plating resist is removed to expose the metal not part of the final circuit pattern. The exposed metal is removed by etching to review the circuit pattern.
As discussed in the article Fluidic Microsystems Based on Printed Circuit Board Technology, J. Micromech. Microeng. 11 (2001) 528-531, Wego, Richter and Pagel, utilization of manufacturing principles of printed circuit boards (PCBs) as, for example, described above, has been suggested to form fluidic microsystems. It is stated therein that the basic idea of PCB-based fluidic systems is to modify the well-known multi-layer technology utilizing conventional, copper plated rigid base metal (e.g., FR4). To create fluidic channels, the PCB is structured (e.g., by chemical wet etching) forming the lateral borders of a channel. By stacking one structured PCB upon another the channel is created.
The cross-sectional view of printhead 10 shows only a single row of nozzles 14. In this design, PCB substrate 16 may be FR4. However, other materials may also be used including but not limited to g10, other polymer materials, plastics, or ceramics. A conductive circuit or trace 18 is patterned on one surface of substrate 12, using known PCB techniques. A body chamber 20 is drilled, lasered, routed, or otherwise formed within substrate 16 using known PCB manufacturing techniques. An inlet 22 is formed within substrate 16 by etching, routing, lasering, drilling or by other known process. Inlet 22 is formed to provide a passage for delivery of ink to body chamber 20.
An actuator metal layer (e.g. diaphragm) 24, such as a stainless steel plate is adhered to a surface of substrate 16 by any of a number of known PCB techniques including the use of lamination and/or adhesives 25. Actuator metal layer 24 could also take the form of a stainless steel shim that is laminated to the PCB board using conventional PCB techniques. A piezoelectric block 26 is bonded to a surface of metal actuator layer 24 by known attachment processes used in the PCB arts, such as by adhesive 25. Piezoelectric block 26 has electrode 28 on a surface which may be formed in known manners such as depositing electrode material over a large block of piezoelectric material (with an electrode) by either a sawing or lasering, and then picking and placing the smaller piezoelectric block (and electrode 28) on actuator layer 24.
Alternatively, and as described in pending U.S. patent application Ser. Nos. 10/375,975, 10/376,527, and 10/376,544 to Baomin Xu, et al., commonly assigned and each incorporated in its entirety by reference, the piezoelectric may be screen printed onto a carrier substrate such as a sapphire substrate, and fired at high temperature. Then it may be laser released for transfer to another substrate, such as in this case the surface of stainless steel layer 24 of
The combination of actuator layer 24 with piezoelectric block 26 (with electrode 28), may be considered a driver mechanism or fluid actuator arrangement. An interconnect, such as wire bond 30, is provided between metal tracing 18 and piezoelectric electrode 28, separated by gap 31. It is to be appreciated other interconnect techniques may be employed such as flip chip or, thin film techniques, among others.
A driver chip 32 such as a driver ASIC may be attached to the PCB and powered by a power supply (not shown).
A nozzle (or aperture) layer 34 (with nozzles 14) is fabricated using current techniques known in the nozzle industry. It may be attached to substrate 16 using conventional PCB lamination or other PCB connection techniques. In one embodiment the nozzle layer is made of stainless steel,which may, for example, be laser drilled, chemically etched or electro formed, and then connected to the substrate 16.
Driver chip 32 is used to provide a selectable signal path for actuation of the ejection process. Driver chip 32, can also provide normalization so that each nozzle in a multi-nozzle system will be individually controlled in its timing of operation, when the driver chip switch closes, allowing current to pass to the intended nozzle.
Therefore in operation of printhead 10, when power is supplied to the driver chip 32, and the driver chip closes a switch to provide a path for a signal from metal trace 18 to wire bond 30 and electrode 28, the piezoelectric block 26 will deform applying pressure to diaphragm 24. Movement of diaphragm 24 into the body chamber 20 causes pressure within the chamber and the ejection of fluid through nozzles 14. Body chamber 20 is replenished with fluid (such as ink) by inlet 22. Inlet 22 is connected to an ink supply such as a manifold, ink reserve or other appropriate external ink source.
With further attention to ink inlet 22, in addition to being formed by routing and drilling, it may also be formed by processes also used to form metal traces 18. In this embodiment the surface of substrate 16 is patterned or masked (e.g., photo-patterning) and etched in step similar to that used to form metal traces intended to carry electrical signals. However in this instance, the etching procedures are used to form fluid passages (such as inlet 22).
For printhead 10 of
It is to be noted that aspects of each of the embodiments of
Inlet 22 is sized so its impedance at the frequency of ejection is sufficient to block backward flow into a reservoir (not shown) of fluid. Therefore, the sizing of inlet 22 is used to control the channel flow.
The embodiments of
In order to obtain a more compact printhead formed on a PCB, multi-layers are attached to each other permitting for the offset of nozzles and of inlets or ink passageways within the printhead. More particularly, by having the multi-layers, it is possible to create multiple passageways for the supply of fluid such as ink to the nozzles, giving a greater degree of freedom than possible in a printhead created of a single printed circuit board.
With more particular attention to
The metal traces may also be used to form fluidic passages, such as passage 98, which connect a fluidic header or manifold formed by lateral cuts 72 and 74. Fluidic passage 98 connects the fluidic header or manifold (72, 74) to the via (e.g., blind via) 78, which forms an ink jet compression chamber.
Metal aperture layer 86 is joined to base 70 by adhesive 88. An aperture hole 100 is shown in layer 86. It is noted, aperture layer 86 could first be attached and thereafter a via or hole made using a process such as a drilling or lasering. Ink will emit from hole 100 as ink droplet 102. The ink is supplied to the printhead via a fitting or other manifold part 104 which is connected to the printhead via a seal such as an O-ring or an epoxy joint 106. The vias may be a fill hole which has the metal around it etched back from the seal area 108 so it does not communicate with the fluid or ink. Adhesive 88 is sufficiently thick and of appropriate properties such that it does not allow electrical connection to the ink. In one embodiment, the connection between piezoelectric block 92 and diaphragm 90 is made by an epoxy or other adhesive 110.
Electrical connections to metal layer 82 and piezoelectric electrode 94 can be made by electrical connections 112, 114 which is accomplished by wire bonds, spring contacts, thin film or other compliant connections. For isolation, metal layer 82 is interrupted by a gap 96 between the point of the wire bond attachment, and the portion of layer 82 that runs under the piezo 94. The former would be the energized signal trace, while the latter would be a ground plane. In this embodiment, the control electronics, such as driver chip 32 of
With continuing attention to
The printhead of
For example, and not intended to be limiting, an additional metal layer may be added on top of metal layer 84, to facilitate more passages or functions. Alternatively, layer 70 itself may not be needed and layer 86 could be bonded straight to layer 84. Still further lateral cut 74 may not be needed as lateral cut 72 may be sufficient.
These blank bases are then stamped, routed, drilled, milled, etched or otherwise processed to create passages in conformance with a predetermined circuit board layout. Eventually, a variety of these passages become the fluidic passages of the printhead (step 134). Openings in the base are created through lateral cuts which form comparatively large openings, while other areas in the layers may include vias (holes) such as tent vias, through-hole vias, and blind vias (step 136). The creation of these lateral cuts and vias are common in printed circu it board manufacture, and may be made by known techniques. Some of the bases may then be connected together using known PCB techniques.
Next, metal layers are joined to the bases using an adhesive process. The adhesives may be any known or developed appropriate adhesive used in the printed circuit board industry (step 138). The joined metal is then masked to define features such as diaphragms and metal traces which are used to carry electrical signals on the multi-layered circuit board. The masking of the metal may also be used to define fluidic passages used to connect the fluidic headers or manifolds to an ink jet compression chamber (as described in
In step 148 two sub-assemblies (as shown in
Ink may be supplied by a connection such as a fitting or other manifold part where a seal such as an O-ring or epoxy connects the manifold part to the printed circuit board (step 150). The metal around the fill hole (as described in connection with
Thereafter, a fluid is filled into the printhead (step 158) and the printhead may be energized to generate droplets (step 160).
By the above outlined processes, a multi-layered printed circuit board printhead is formed. Thus, by modifying well known multi-layer PCB technology utilizing conventional double-sided plated rigid base materials, it is possible to form a printhead with fluidic chambers, fluidic passages, electrical connections, nozzles and control on the multi-layered PCB. It is to be appreciated the forgoing order of steps may be altered and additional steps added or existing steps eliminated depending on the printhead being manufactured.
With further attention to the formation of the fluidic channels, a particular issue is to ensure that the adhesive between the multi-layers does not interfere with the interior of the fluidic channels. One embodiment has been discussed in connection with
Another procedure is suggested in the article, Fluidic Microsystems Based On Printed Circuit Board Technology, Institute of Physics Publishing J. Micromech. Microeng., 11 (2001) 528-531”. In this process a single board dipped in an adhesive liquid of a certain viscosity (epoxy resin solved in ethanol, the viscosity approximately equals 3-7 mPa s) and coated with a thin uniform adhesive film (2-6 μm) by pulling them out of the solution with a constant velocity. Subsequently, the adhesive is cured under the application of temperature and pressure. This technique is described as ensuring a tight connection of the PCBs and will maintain the fluidic functionality of the channels without reducing the channel height significantly (2-6 μm).
In another embodiment the fluidic passages may be defined by the base material (e.g., FR4) being located on all sides so there would not be any patterned copper or other metal within the interior of the fluidic passage. Particularly, the base material may be milled or routed using an end mill router or laser to form a particular side of the passage. Then when the pieces are brought together (i.e., the individual base layers of the multi-layer circuit board) the passage will be defined only by the base layer material by this process, the adhesive (e.g., epoxy) issue is still relevant, but there will not be wetted metal such as copper to address. So in this case, instead of the passage being a place where the metal is etched away, the milling, routing, etc. operations will provide an indentation within the base without the etching process being necessary.
In some embodiments certain high value custom printhead layers such as the top layer of stainless steel (e.g., the aperture layer), and the bottom layer of stainless steel (e.g., the diaphragm) may be processed separately from the PCB processes and laminated to the circuit board. These stainless steel layers may be laser drilled, chemical etched, electro formed or manufactured by other known processes and then bonded to the nearly complete printed circuit board structure.
Turning now to
The printhead of
An integrated circuit chip such as an ASIC may be attached on multi-layered PCB 170 whereby all components of the printhead are located on the printed circuit board. However, this diagram is also intended to show that at least some components of the printhead do not need to be on the printed circuit board. For example, the ASIC may be located external to the board and simply electrical connection lines would be provided to send the required signals for appropriate droplet ejection.
Ink entering ink inlet 182 flows into ink supply manifold 186. A typical ink jet printhead of this type has at least four such manifolds for receiving, respectively, black, cyan, magenta, and yellow ink for use in black plus three color subtraction printing. However, the number of such manifolds may be varied depending upon whether a printer is designed to print solely in black ink or with less than a full range of color. From ink supply manifold 186, ink flows through ink supply channel 188, through ink inlet 190 and into ink pressure chamber 192. Ink leaves pressure chamber 192 by way of ink pressure chamber outlet 194 and flows through ink passage 196 to nozzle 184 from which ink drops are ejected. Arrows 198 diagram this ink flow path.
Ink pressure chamber 192 is bounded on one side by metal trace 200 which includes an area acting as a flexible diaphragm 200′. The pressure transducer in this case is piezoelectric block 202 secured in a manner as described in previous embodiments. Piezoelectric block 202 includes metal film layer (electrode) 202 a to which an integrated electronic circuit drive (e.g., an ASIC 203), is electrically connected by connector arrangement 204. The ASIC 203 is electrically connected to metal trace 200, wherein metal trace 200 has a gap portion 205 for electrical isolation. Application of power by a power source (not shown) causes a bending in piezoelectric block 202 which displaces ink in ink chamber 192. Refill of ink chamber 192 following the ejection of an link drop can be augmented by reverse bending of piezoelectric block 202. As shown in
In addition to main ink flow path 198 described above, optional ink outlet or purging channel 206 is also defined. The purging channel 206 is coupled to the ink passage 196 at a location adjacent to but interior of nozzles 184. The purging channel communicates from passage 196 to outlet or purging manifold 208 which is connected by outlet passage 210 to purging control outlet port 212. The manifold 208 is typically connected by similar purging channels 206 to the passages associated with multiple nozles. During this purging operation, ink flows in a direction indicated by arrows 214 through purging channel 206, manifold 208 and purging passage 210.
As described in the previous embodiments, the various interior fluidic passages are formed using the previously-discussed PCB techniques of routing, milling, laser cutting, drilling as well as etching of metal traces such as copper traces. Thus, the copper traces may be used for electrical connection as described as well as the formation of fluidic channels. As can be seen in this embodiment, there are multiple PCB substrate layers in which the passages as well as metal tracings are formed. The combination of the layers or bonding of the layers occurs as in the previous embodiments including the appropriate PCB adhesives and other bonding procedures well known in the PCB arts. Thus,
As stated above, while a cross-section of this figure is shown, multiple nozzles are provided with the liquid passageways formed within the printed circuit board as discussed in the previous embodiments.
While the foregoing description has primarily discussed ejection of ink and ink printing, the described devices and methods may be used for applications other than ink printing, such as for use in the areas of biology, combinatorial chemistry, as well as other areas, for ejection of biofluids or combinatorial materials. Thus, the foregoing is not limited to image or document printing.
Although the present concepts have been described herein with reference to specific embodiments, many modifications and variations therein will readily occur to those skilled in the art. Accordingly, all such variations and modifications are included within the intended scope of the following claims.
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|U.S. Classification||347/50, 347/58|
|International Classification||B41J2/16, B41J2/14|
|Cooperative Classification||H05K1/0272, B41J2/14233, H01L2224/73265, B41J2202/12, H01L2224/48091, H05K2201/0394, B41J2002/14491, H05K2201/10083|
|European Classification||H05K1/02F, B41J2/14D2|
|Dec 20, 2004||AS||Assignment|
Owner name: PALO ALTO RESEARCH CENTER INCORPORATED, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ELROD, SCOTT A.;FITCH, JOHN S.;BIEGELSEN, DAVID K.;REEL/FRAME:016122/0293;SIGNING DATES FROM 20041213 TO 20041214
|Jul 20, 2011||FPAY||Fee payment|
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Year of fee payment: 8